Progressing cavity pumps and motors have been used for decades in pumping applications and in hydraulic motor applications. A conventional progressing cavity pump consists of a rigid rotor having a contoured interior surface along an axial length thereof. The interior surface of the rotor mates with the exterior surface of a rotor which has a contoured exterior surface, with one additional lead on the interior of the stator. This lead difference forms cavities between the rotor and the stator which are continually progressing from one end of the stator to the other when the rotor is turning. Operation of a pump is achieved by mechanically turning the rotor, while operation of a motor is achieved by forcing fluid into one end of the stator to turn the rotor. An elastomeric or plastic material is conventionally bonded to the rigid stator tube, thereby providing a fluid tight seal between the elastomeric stator material and the outer tubular housing.
In some applications, a progressing cavity pump has an extremely long length, e.g., thirty feet or more, which makes transportation and handling of the stator difficult. During manufacturing, an elongate rotor in two or more pieces may be assembled end-to-end at the manufacturing plant using appropriate jigs. The end of one rotor section may thus be aligned with the adjacent end of another rotor section, so that rotor sections are rotationally aligned when welded together. Such direct alignment of a motor/pump housing is difficult to envision with the structural and functional requirements of a pump/motor. More specifically, the elongate stator of a pump/motor is preferably connected in the field, and does not require welding at the rig site or the use of specialized jigs.
The disadvantages of the prior art are overcome by the present invention, and an improved progressing cavity pump/motor with upper and lower stator sections and a coupling assembly for interconnecting these sections is hereinafter disclosed.